Shale oil refining process



Oct. 19, 1954 O( L SHALE- W. M. SMITH SHALE OIL REFINING PROCESS Filed001;. 7, 1950 QETOQTING HYDRO- 65 N ATOR,

ACHD

TQEATING PLANT Patented Oct. 19, 1954 SHALE OIL REFINING PROCESS WarrenM. Smith, Baton Rouge, La., assignor to Standard Oil DevelopmentCompany, a corporation of Delaware Application October 7, 1950, SerialNo. 188,960

Claims.

The present invention relates to an improved process for the recovery ofvaluable fuels including gasoline, gas oil, and fuel oil rangehydrocarbons by the distillation of oil-bearing minerals, particularlyoil shale, wherein the raw solids are retorted, preferably in the formof subdivided particles maintained in a highly turbulent state fluidizedby upwardly flowing gases to resemble a boiling liquid, and thedistillate produced is subjected to a refining treatment to isolateproducts of the type mentioned above. More particularly, the inventionrelates to improvements in the refining stage whereby increasedoperational efficiency and higher quality products in higher yields areobtained.

Organic matter in oil shale is believed to exist in the form of kerogen,a solid consisting of hydrocarbons in combination with sulfur, nitrogen,and oxygen, thus difiering from crude petroleum,

which exists as such in the pores of porous sands.

Crude shale oil produced from the oil shale by decomposition of thekerogen by means of heat also differs from crude petroleum mainly in itsextremely high content of nitrogen compounds which probably areresponsible for its poor color stability and its disagreeable odor. Itis this property of crude shale oil which requires additional treatingwhen shale oil is refined by conventional petroleum refining techniquesand procedures.

Established shale oil refining procedures generally involve acombination of distillation for separation of crude shale oil into thevarious boiling range products, and treatment of these products withsulfuric acid for removal of nitrogen compounds. Such chemical refiningtreatment must of necessity be very carefully controlled in order toprevent excessive losses of valuable reactive unsaturated hydrocarbonswhich occur in shale oil as a result of the destructive distillation ofthe kerogen. In an attempt to minimize treating losses and therebypreserve volume, since crude shale oil is a relatively expensive rawmaterial when compared with present day crude petroleum, it has beenproposed to hydrogenate the total crude shale oil mainly in order toreduce the sulfur and nitrogen content to the levels usually met with incrude petroleum, in order to produce a refined shale oil which wouldthen be amenable to further processing by conventional crude refiningtechniques, as cracking, reforming, etc. Hydrogenation of the shale oilwas found to effect some improvement in odor and color. At lower levelsof hydrogenation, it was found that the hydrogenated products tended todarken on standing in contact with air. Color stability was found toincrease with increase in degree of hydrogenation, but this requiredexcessive amounts of hydrogen, and tended to increase the cost of theprocess.

It is the principal object of the present invention to disclose animproved economic process for refining shale oil without excessive useof hydrogen.

It is also an object of the present invention to disclose a chemicalprocess for treating shale oil wherein losses due to sludge formationare minimized.

Other objects and advantages of the present invention will becomeapparent from the more detailed description hereinafter.

It has now been found that the above advantages and results may beachieved by hydrogenating the crude shale only to the point wherein thereactive olefinic hydrocarbons are saturated and some of the nitrogencompounds decomposed to ammonia and hydrocarbons or to more basic typenitrogen compounds, and then subjecting the resulting product to arelatively light acid treat. By operating in accordance with thisprocess, it has been found that only small treating losses occur duringthe acid treatment, as against large losses when the unhydrogenatedcrude shale is acid treated. On the other hand, by restrictinghydrogenation only to the saturation of the olefins and a mildhydrogenation of the nitrogen compounds, large quantities of hydrogenand expensive hydrogenation equipment are minimized. Again,hydrogenation alone, particularly of the low boiling fractions, did notproduce a color and odor-stable product in the presence of air, but, inaccordance with the present invention, when the hydrogenated product wasgiven a light acid treat, color stability and improvement were achievedwith relatively little loss in product, due to the material being newhighly saturated.

The invention may be more clearly understood when read in conjunctionwith the attached drawing which is a diagrammatic representation ofpreferred embodiments of the invention. Referring now to the figure,crude shale oil resulting from the retorting of oil shale by anyconventional means, preferably by the fluid solids technique, is passedfrom the distillation and retorting sections to the refinin section.Crude shale oil and distillate, as stated above, are customarilysubjected to conventional refining treatments, such as thermal orcatalytic cracking, alkylation, polymerization, isomerization,hydroforming, dehydrogenation, etc. by methods known to the petroleumrefining art. However, these refining procedures are detrimentallyaffected by the high nitrogen and sulfur contents of the shale oil, and,in accordance with the present invention, the total oil product from theefiluent is hydrogenated and then acid treated.

The total effluent from the oil shale distilla tion retort it may bepassed to a hydrogenation vessel i2, wherein the olefins present in thetotal product are hydrogenated and the nitrogen compounds mildlyhydrogenated to produce some ammonia and some more basic type nitrogencompounds. If desired, a mild vis-breaking treatment to decrease the oilviscosity and pour point, may follow the retorting operation,particularly if the shale oil must be transferred a considerabledistance to the refining site. A good hydrogenation catalyst is composedof the mixed sulphides of nickel and tungsten or nickel and molybdenum.Hydrogenation over these catalysts gives a product of considerablydecreased olefinicity together with some lowering of nitrogen and sulfurcontent. Hydrogenation may be accomplished with satisfactory catalystlife at about 2000 to 4000 p. s. i. g., for instance at 3000 p. s. i. g.and temperatures of about 700 to 800 F., depending upon the degree ofhydrogenation desired. Space velocities of from 0.5 to 2 v./v./hr. atthese conditions are satisfactory, while hydrogen consumption rates aremaintained at a level about 500 to 1500 cubic feet of hydrogen perbarrel oil fed.

The partially hydrogenated material which is now highly saturated, outwhich may still contain significant quantities of sulfur and nitrogenimpurities, is then passed via line i l to acid treater it, wherein thesaturated crude shale oil is contacted preferably with sulfuric acid.Treating conditions preferably include temperatures of from 50 to 100 F.and acid/oil ratios of about 2 to 20 pounds concentrated H2504 perbarrel of hydrogenated oil. Other treating min oral acids, such as IiBPOl, may be employed.

The acid treated hydrogenated shale oil with its sulfur and nitrogencontent considerably reduced as a result of the combined hydrogenationand acid treatment, is now passed from treater it to the shale oilrefining plant for further conversion as is customary in the petroleumrefining operation, such as distillation, cracking, hydroforming,reforming, etc., all in a manner known per se.

Instead of treating the total crude shale product to thehydrogenation-acid treating process, it may under certain circumstances,be desirable'to separate the crude shale oil by distillation intoappropriate fractions, such as a gasoline and gas oil fraction andhigher boiling fractions, and separately hydrogenate and acid treat therespective cuts. genate the total crude shale oil resulting from theretorting operation, then fractionate into the desired products andseparately acid treat the resulting cuts.

' The superior results obtained by partially hydrogenating the crudeshale oil and following this treatment with a light acid treat may beillustrated by the following specific example.

In the above runs, the crude shale oil was hydrogenated to the extent of1400 cubic feet of Or, if desired, one may also hydro- 4 H2 per barrelof oil. The acid treating was light, 5 pounds of 98% H2SO'4 beingemployed per barrel of oil.

Hydrogenation alone results in some increase in volatility of the shaleoil at the expense of the 700 F.+ fraction, and also considerableremoval of nitrogen as ammonia. In addition, hydrogenation convertsresidual nitrogen compounds apparently into a form more readily amenableto removal by acid extraction.

The color stability of the diesel fuel fraction prior to acid treatmentwas unsatisfactory, but by the acid treat it was put into form meetingestablished specifications. As for the color of the gasoline fraction,this was lower than normal but, since its volume is low, it may readilybe blended ofi. Alternatively, a slightly greater acid treat may beemployed, whereby an improved color (water white 01' +30 Saybolt) wouldbe obtained.

The example shows, therefore, that at even the moderately high hydrogenconsumption level of M00 cubic feet per barrel, the preparation ofdistillate fuel of satisfactory quality by distillation alone was notpossible, but that by the use of a light acid wash, a considerableimprovement was obtained without significant loss in yield. In order toobtain products of comparable characteristics from the crude shale oilalone without an intermediate hydrogenation step, a much more severeacid treatment would be required and a considerably greater loss inyield would result.

Various modifications of the system described above may occur to thoseskilled in the art Without deviating from the spirit of the invention.The above description and exemplary operations have served to illustratespecific embodiments of the invention but are not intended to belimiting in scope.

What is claimed is:

1. In the process of producing oil from oil shale by subjecting the oilshale to distillation temperatures in a distillation zone and recoveringthe crude oil distillate comprising olefinic hydrocarbons and nitrogenand sulfur compounds from said distillation Zone, the improvement whichconsists essentially of contacting at least a portion of said distillatein a hydrogenation zone at a space velocity of about 0.5 to 2 v./v./hr.,a pressure of about 2000 to 4000 p. s. i. g., and temperatures of about700 to 800 F. with hydrogen in the presence of a nickel sulfidecontaining hydrogenation catalyst until up to about 1500 cubic feet ofhydrogen is consumed per barrel of oil, whereby said olefinichydrocarbons are substantially saturated and nitrogen compoundspartially hydrogenated, passing said hydrogenated material to an acidtreating zone, contacting said material with a minor amount of acidselected from the group consisting of sulfuric and phosphoric acid, andrecovering high yields of superior liquid fuel.

2. The process of claim 1 wherein said acid is H2SO4.

3. The process of claim 2 wherein said acid is added to said oil in theratio of about 2 to 20 pounds of 98% H2SO4 per barrel of oil.

4. The process of claim 1 wherein said hydrogenation catalyst is a mixedsulfide of nickel and a metal selected from the group consistingoftungsten and molybdenum.

5. In a process for improving a crude shale oil containing olefinichydrocarbons as Well as nitrogen and sulfur compounds, the improvementwhich consists essentially of passing at least a portion of said crudeshale oil to a i=hydrogena-- tion zone at a space velocity of about 0. 5to 2.0 v./v./hr., contacting said oil in said hydrogenation zone with anickel sulfide containing hydrogenation catalyst in the presence ofhydrogen at a pressure of about 2000-4000 p. s. i. g. and at atemperature of about ZOO-800 F. until about 500-1500 cubic feet ofhydrogen are consumed per barrel of oil feed, passing the resultinghydrogenated oil to an acid treating zone, mixing the hydrogenated oilwith concentrated sulfuric acid in a ratio of about 2 to 20 lbs. of acidper barrel of oil, separating the acid treated oil from the mixture anddistilling the separated oil to isolate therefrom a gas oil having agreatly reduced nitrogen content.

6. A process according to claim 5 wherein the catalyst is a mixedsulfide of nickel and a metal selected from the group consisting oftungsten and molybdenum.

7. A process according to claim 6 wherein the shale oil being treated isa diesel fuel fraction having a boiling range between 400 and 700 F.

8. A process according to claim 6 wherein the shale oil being treated isa gasoline fraction having an end point of about 400 F.

9. A process according to claim 5 wherein the feed to the hydrogenationzone is the total crude oil obtained by distillation of an oil shale.

10. A process according to claim 9 wherein 98% sulfuric acid is used ina ratio of about 5 lbs. per barrel of oil treated.

References Cited in the file of this patent UNITED STATES PATENTS INumber Name Date 2,106,013 Ocon Jan. 18, 1938 2,206,200 Ocon July 2,1940 2,242,504 Benedict et al May 20, 1941 OTHER REFERENCES Kalichevskyet al., Chemical Refining of Petroleum, Reinhold Publishing Corp.(1942), pages 49, 57, 59.

1. IN THE PROCESS OF PRODUCING OIL FROM OIL SHALE BY SUBJECTING THE OILSHALE TO DISTILLATION TEMPERATURES IN A DISTILLATION ZONE AND RECOVERINGTHE CRUDE OIL DISTILLATE COMPRISING OLEFINIC HYDROCARBONS AND NITROGENAND SULFUR COMPOUNDS FROM SAID DISTILLATION ZONE, THE IMPROVEMENT WHICHCONSISTS ESSENTIALLY OF CONTACTING AT LEAST A PORTION SAID DISTILLATE INA HYDROGENATION ZONE AT A SPACE VELOCITY OF ABOUT 0.5 TO 2V./V./HR., APRESSURE OF ABOUT 2000 TO 4000 P. S. I. G., AND TEMPERATURES OF ABOUT700 TO 800* F. WITH HYDROGEN IN THE PRESENCE OF A NICKEL SULFIDECONTAINING HYDROGENATION CATALYST UNTIL UP TO ABOUT 1500 CUBIC FEET OFHYDROGEN IS CONSUMED PER BARREL OF OIL, WHEREBY SAID OLEFINICHYDROCARBONS ARE SUBSTANTIALLY SATURATED AND NITROGEN COMPOUNDSPARTIALLY HYDROGENATED, PASSING SAID HYDROGENATED MATERIAL TO AN ACIDTREATING ZONE, CONTACTING SAID MATERIAL WITH A MINOR AMOUNT OF ACIDSELECTED FROM THE GROUP CONSISTING OF SULFURIC AND PHOSPHORIC ACID, ANDRECOVERING HIGH YIELDS OF SUPERIOR LIQUID FUEL.